In recent years, a new technical field which is called flexible electronics has attracted much attention. This technology is for realizing mechanical flexibility in electronics, and is different from a technical trend of microfabrication in the related art. In particular, flexible electronics is considered as a technology having important value for large-volume electronics, such as a display, a solar battery, a sensor, or an actuator.
For example, as the size of an electronics device increases, flexibility becomes indispensable for portability or impact resistance. A difficulty after realizing flexible electronics lies in achieving having both electrical properties and mechanical properties which are excellent in a plastic film.
Stretchability of an electronics device is considered a function which is necessary for the electronics device to be integrated with a structure or a living body which is deformed according to movement or application of weight thereto. In order to realize a device having stretchability, it is necessary that an active circuit, such as a transistor which configures the device, and a passive circuit, such as a resistor or a capacitor, have a configuration in which damage is not received, and a configuration in which properties do not change according to deformation of the device.
However, a transistor made of an inorganic material typified by silicon, is made of a material which does not have stretchability, such as silicon or an inorganic oxide material, and cracks are generated in these materials under a strain which is much less than 1%. In addition, in an organic transistor using an organic semiconductor which has a carbon main skeleton, there are no cases where a breakage is generated even under a strain which is approximately 1% as the organic material is soft and has ductility, and in a case where the organic transistor is formed on a film-like substrate, the organic transistor is effective in realizing a highly flexible device under bending deformation.
In addition, in order to attach a film-like device such that the device adheres tightly to a surface of a three-dimensional object, it is necessary for the device to be not only flexible but also stretchable. In addition, for a device film for sticking a device on the surface of a robot or a human being, particularly on the surface of a joint portion, it is necessary for the film to be compatible with being extended by several tens of %.
Here, in the related art, a configuration in which a flexible sensor provided with a field effect type transistor integrated circuit can be attached to a part of a human body is provided, and research using the sensor as a pressure sensitive sensor has been carried out (refer to Non-Patent Document 1). In this research, a flexible circuit which can be folded using an organic field effect transistor (OFET) is realized, and an electronic artificial skin in which a pressure sensitive sensor array and a peripheral circuit which are effective as area sensors, such as tactile sensor, are integrated, has been made as a prototype.
Specifically, a pressure sensor is configured by forming a plurality of organic transistors on a film made of a flexible resin in a matrix form, and by layering a sheet of a pressure sensitive conductive rubber, a resin film having an electrode, and a film made of resin provided with through holes having lands at a predetermined pitch thereon.